Optical tube assembly having a dry insert and methods of making the same

ABSTRACT

An optical tube assembly and methods of manufacturing the same include a tube, at least one optical waveguide, and a dry insert. In one embodiment, the dry insert generally surrounds the at least one optical waveguide and forms a core that is disposed within the tube. In one embodiment, the dry insert is compressed at least about 10 percent for coupling the at least optical waveguide to the interior surface of the tube.

FIELD OF THE INVENTION

The present invention relates generally to dry packaging of opticalwaveguides. More specifically, the invention relates to an optical tubeassembly that includes at least one dry insert for protecting at leastone optical waveguide.

BACKGROUND OF THE INVENTION

Fiber optic cables include optical waveguides such as optical fibersthat transmit optical signals, for example, voice, video, and/or datainformation. One type of fiber optic cable configuration includes anoptical waveguide disposed within a tube, thereby forming a tubeassembly. Generally speaking, the tube protects the optical waveguide;however, the optical waveguide must be further protected within thetube. For instance, the optical waveguide should have some relativemovement between the optical waveguide and the tube to accommodatebending. On the other hand, the optical waveguide should be adequatelycoupled with the tube, thereby inhibiting the optical waveguide frombeing displaced within the tube when, for example, pulling forces areapplied to install the cable. Additionally, the tube assembly shouldinhibit the migration of water therein. Moreover, the tube assemblyshould be able to operate over a range of temperatures without undueoptical performance degradation.

Conventional optical tube assemblies meet these requirements by fillingthe tube with a thixotropic material such as grease. Thixotropicmaterials generally allow for adequate movement between the opticalwaveguide and the tube, cushioning, and coupling of the opticalwaveguide. Additionally, thixotropic materials are effective forblocking the migration of water within the tube. However, thethixotropic material must be cleaned from the optical waveguide beforeconnectorization of the same. Cleaning the thixotropic material from theoptical waveguide is a messy and time-consuming process. Moreover, theviscosity of thixotropic materials is generally temperature dependent.Due to changing viscosity, the thixotropic materials can drip from anend of the tube at relatively high temperatures and the thixotropicmaterials may cause optical attenuation at relatively low temperatures.

Cable designs have attempted to eliminate thixotropic materials from thetube, but the designs are generally inadequate because they do not meetall of the requirements and/or are expensive to manufacture. One examplethat eliminates the thixotropic material from the tube is U.S. Pat. No.4,909,592, which discloses a tube having water-swellable tapes and/oryarns disposed therein. This design requires a large number ofwater-swellable components within the tube to adequately couple opticalfibers to the tube. The use of large numbers of water-swellablecomponents is not economical because it increases the cost of the cable.Another example that eliminates the thixotropic material is U.S. Pat.No. 6,278,826, which discloses a foam having a moisture content greaterthan zero that is loaded with superabsorbent polymers. The moisturecontent of the foam is described as improving the flame-retardantcharacteristics of the foam. Likewise, the foam of this design isrelatively expensive and increases the cost of the cable.

SUMMARY OF THE INVENTION

The present invention is directed to an optical tube assembly includinga tube having an interior surface, at least one optical waveguidedisposed within the tube, and at least one dry insert. The dry insertbeing disposed within the tube and generally surrounding the at leastone optical waveguide. The dry insert is compressed at least about 10percent for adequately coupling the at least one optical waveguide tothe interior surface of the tube. Moreover, optical cables according tothe present invention can include one, or more, optical tube assembliesas described herein.

The present invention is also directed to an optical tube assemblyincluding a tube having an interior surface, at least one opticalwaveguide, and at least one dry insert. The at least one dry inserthaving at least two laminated layers that generally surround the atleast one optical waveguide, thereby forming a core that is disposedwithin the tube. The at least one dry insert is capable of adequatelycoupling the at least one optical waveguide to the interior surface ofthe tube while cushioning the at least one optical waveguide, therebymaintaining an optical attenuation below about 0.3 dB/km at a referencewavelength of 1550 nm.

The present invention is further directed to an optical tube assemblyincluding a tube having an interior surface, at least one opticalwaveguide, and at least one dry insert. The at least one dry insert andthe at least one optical waveguide forming a core disposed within thetube, wherein the at least one optical waveguide has a normalizedpull-out force between about 0.5 N/m and about 5.0 N/m.

Additionally, the present invention is directed to a method ofmanufacturing an optical tube assembly including the steps of paying offat least one optical waveguide. Placing a dry insert adjacent to the atleast one waveguide, thereby forming a core. Extruding a tube around thecore so that the core has a normalized pullout force between about 0.5N/m and about 5.0 N/m.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view of a tube assembly according to thepresent invention.

FIG. 2 is a cross-sectional view of the dry insert of the tube assemblyof FIG. 1.

FIG. 3 is a bar graph depicting an optical ribbon pull-out force forvarious tube configurations.

FIG. 4 is a schematic representation of a manufacturing line accordingto the present invention.

FIG. 5 is a cross-sectional view of a fiber optic cable according to oneembodiment of the present invention.

FIG. 6 is a graph depicting an optical ribbon coupling force associatedwith various cable configurations.

FIG. 7 is a perspective view of another dry insert according to theconcepts of the present invention.

FIG. 8 is a cross-sectional view of another dry insert according to theconcepts of the present invention.

FIG. 9 is a perspective view of another dry insert according to theconcepts of the present invention.

FIG. 10 is a perspective view of another dry insert according to theconcepts of the present invention.

FIG. 11 is a cross-sectional view of a cable having a conventionalgrease filled tube assembly.

FIG. 12 is a cross-sectional view of a cable having a conventional drytube assembly.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings showing preferred embodiments ofthe invention. The invention may, however, be embodied in many differentforms and should not be construed as limited to the embodiments setforth herein; rather, these embodiments are provided so that thedisclosure will fully convey the scope of the invention to those skilledin the art. The drawings are not necessarily drawn to scale but areconfigured to clearly illustrate the invention.

Illustrated in FIG. 1 is an exemplary tube assembly 10 according to oneaspect of the present invention. Tube assembly 10 includes at least oneoptical waveguide 12, at least one dry insert 14, and a tube 18. In thiscase, the at least one optical waveguide 12 is in the form of a stack ofribbons having a diagonal D dimension across the corners of the stack.Dry insert 14 generally surrounds the at least one optical waveguide 12and forms core 15, which is disposed within tube 18. Dry insert 14performs functions such as cushioning, coupling, inhibiting themigration of water, and accommodates bending. Dry insert 14 isadvantageous because the optical waveguides are easily removed therefromwithout leaving a residue or film that requires cleaning beforeconnectorization. Moreover, unlike conventional thixotropic materials,dry insert 14 does not change viscosity with temperature variations orhave a propensity to drip from an end of the tube at high temperatures.Furthermore, tube assembly 10 can include other suitable components suchas a polyester binder thread 17 to hold dry insert 14 about opticalwaveguide 12. Additionally, tube assembly 10 can be a portion of cableas shown in FIG. 5.

As depicted, optical waveguide 12 is an optical fiber that forms aportion of an optical fiber ribbon. In this case, the optical waveguidesare a plurality of single-mode optical fibers in a ribbon format thatform a portion of a ribbon stack. The ribbon stack can include helicalor S-Z stranding. Additionally, other types or configurations of opticalwaveguides can be used. For example, optical waveguide 12 can bemulti-mode, pure-mode, erbium doped, polarization-maintaining fiber,other suitable types of light waveguides, and/or combinations thereof.Moreover, optical waveguide 12 can be loose or in bundles. Each opticalwaveguide 12 may include a silica-based core that is operative totransmit light and is surrounded by a silica-based cladding having alower index of refraction than the core. Additionally, one or morecoatings can be applied to optical waveguide 12. For example, a softprimary coating surrounds the cladding, and a relatively rigid secondarycoating surrounds the primary coating. Optical waveguide 12 can alsoinclude an identifying means such as ink or other suitable indicia foridentification. Suitable optical fibers are commercially available fromCorning Incorporated of Corning, N.Y.

FIG. 2 illustrates a cross-sectional view of dry insert 14. Dry insert14 is formed from an elongate material or materials that are capable ofbeing paid off from a reel for a continuous application duringmanufacture. Dry insert 14 is preferably formed from a plurality oflayers that can perform different functions; however, the dry insert canbe a single layer such as a compressible layer. Dry insert 14 cushionsoptical waveguide 12 from tube 18, thereby maintaining opticalattenuation of optical waveguide 12 below about 0.4 dB/km at a referencewavelength of 1310 nm and 0.3 dB/km at a reference wavelengths of 1550nm and 1625 nm. In one embodiment, dry insert 14 is formed from twodistinct layers. For instance, a first layer 14 a of dry insert 14 is acompressible layer and second layer 14 b is a water-swellable layer.First layer 14 a is formed from a compressible material having apredetermined spring constant for providing adequate couplingcharacteristics. By way of example, the first layer is a foam tape,preferably, an open cell foam tape; however, any suitable compressiblematerial can be used such as a closed cell foam tape. First layer 14 amay be compressed during assembly so that it provides a predeterminednormal force that inhibits optical waveguide 12 from being easilydisplaced longitudinally along tube 18. Dry insert 14 preferably has anuncompressed height h of about 5 mm or less for minimizing the tubediameter and/or cable diameter; however, any suitable height h can beused for dry insert 14. Additionally, height h of dry insert 14 need notbe constant across the width, but can vary, thereby conforming to thecross-sectional shape of the optical waveguides and providing improvedcushioning to improve optical performance (FIG. 10). Second layer 14 bis a water-swellable layer such as a tape that inhibits the migration ofwater within tube 18.

Compression of dry insert 14 is actually a localized maximum compressionof dry insert 14. In the case of FIG. 1, the localized maximumcompression of dry insert 14 occurs at the corners of the ribbon stackacross the diameter. Calculating the percentage of compresssion of dryinsert 14 in FIG. 1 requires knowing an inner diameter of tube 18, adiagonal D dimension of the ribbon stack, and an uncompressed height hof dry insert 14. By way of example, inner diameter of tube 18 is 7.1mm, diagonal D of the ribbon stack is 5.1 mm, and the uncompressedheight h of dry insert 14 across a diameter is 3.0 mm (2 times 1.5 mm).Adding diagonal D (5.1 mm) and the uncompressed height h of dry insert14 across the diameter (3.0 mm) yields an uncompressed dimension of 8.1mm. When placing the ribbon stack and dry insert 14 and into tube 18with an inner diameter of 7.1 mm, dry insert is compressed a total of 1mm (8.1 mm-7.1 mm). Thus, dry insert 14 is compressed by about thirtypercent across the diameter of tube 18.

In other embodiments, first layer 14 a is uncompressed, but begins tocompress if optical waveguide movement is initiated. Other variationsinclude attaching or bonding a portion of dry insert 14 to tube 18. Forexample, adhesives, glues, elastomers, and/or polymers 14 c are disposedon a portion of the surface of dry insert 14 that contacts tube 18 forattaching dry insert 14 to tube 18. Additionally, it is possible tohelically wrap dry insert 14 about optical waveguide 12, instead ofbeing longitudinally disposed. In still further embodiments, two or moredry inserts can be formed about optical waveguide 12 such as two halves.

FIG. 3 is a bar graph depicting a normalized optical ribbon pulloutforce (N/m) for various tube configurations. The ribbon pullout forcetest measured the force required to initiate movement of a ribbon stackfrom a 10-meter length of cable. Specifically, the stack of ribbons werepulled from the tube and the force required to initiate movement wasdivided by the length of the cable, thereby normalizing the opticalribbon pull-out force. As a baseline for comparison, bar 30 depicts aribbon pullout force of about 4.8 N/m for a ribbon stack of 120-fibersin conventional grease (a thixotropic material) filled tube (FIG. 11).Bar 32 depicts a ribbon pullout force for a conventional dry tube designsolely having a water-swellable tape around a ribbon stack of 144-fibers(FIG. 12), which are loosely disposed in a tube. Specifically, bar 32depicts a ribbon pullout force of about 0.6 N/m for the 144-fiber ribbonstack. Thus, the conventional dry tube design (FIG. 12) has a ribbonpullout force that is about twelve percent of the ribbon pullout forceof the conventional grease filled tube (FIG. 11), which is inadequatefor proper cable performance.

Bars 34, 36, and 38 represent tube assemblies according to the presentinvention. Specifically, bar 34 depicts a ribbon pullout force of a144-fiber stack from a tube assembly 10 having dry insert 14 with anuncompressed height h of about 1.5 mm with about a zero percentcompression of dry insert 14. In this embodiment, bar 34 depicts aribbon pullout force of about 1.0 N/m, which is a surprising improvementover the conventional dry tube. Bars 36 and 38 represent configurationswhere dry insert 14 is compressed within tube assembly 10 by apercentage from its original height to an average compressed height.More specifically, bar 36 represents a ribbon pullout force of a similartube assembly as bar 34, expect that in this embodiment dry insert 14 iscompressed about thirty percent. In this embodiment, bar 36 depicts aribbon pullout force of about 2.7 N/m. Bar 38 represents a ribbonpullout force of a 144-fiber ribbon stack from a tube assembly with dryinsert 14 having an uncompressed height h of about 3 mm, which iscompressed by about thirty percent within the tube. In this embodiment,bar 38 depicts a ribbon pullout force of about 0.5 N/m. Thus, accordingto the concepts of the present invention the compression of dry insert14 is preferably in the range of about 10% to about 90%; however, othersuitable ranges of compression may provide the desired performance.Nonetheless, the compression of dry insert 14 should not be so great asto cause undue optical attenuation in any of the optical waveguides.Preferably, the ribbon pullout force is in the range of about 0.5 N/mand about 5.0 N/m, more preferably, in the range of about 1 N/m to about4 N/m.

FIG. 4 schematically illustrates an exemplary manufacturing line 40 fortube assembly 10 according to the present invention. Manufacturing line40 includes at least one optical waveguide payoff reel 41, a dry insertpayoff reel 42, a compression station 43, a binding station 44, across-head extruder 45, a water trough 46, and a take-up reel 49.Additionally, tube assembly 10 may have a sheath 20 therearound, therebyforming a cable 50 as illustrated in FIG. 5. Sheath 20 can includestrength members 19 a and a jacket 19 b, which can be manufactured onthe same line as tube assembly 10 or on a second manufacturing line. Theexemplary manufacturing process includes paying-off at least one opticalwaveguide 12 and dry insert 14 from respective reels 41 and 42. Only onepayoff reel for optical waveguide 12 and dry insert 14 are shown forclarity; however, the manufacturing line can include any suitable numberof payoff reels to manufacture tube assemblies and cables according tothe present invention. Next, dry insert 14 is compressed to apredetermined height h at compression station 43 and generallypositioned around optical waveguide 12, then binding station wraps abinding thread around dry insert 14, thereby forming core 15.Thereafter, core 15 is feed into cross-head extruder 45 where tube 18 isextruded about core 15, thereby forming tube assembly 10. Tube 18 isthen quenched in water trough 46 and then tube assembly 10 is wound ontotake-up reel 49. As depicted in the dashed box, if one manufacturingline is set-up to make cable 50, then strength members 19 a are paid-offreel 47 and positioned adjacent to tube 18, and jacket 19 b is extrudedabout strength members 19 a and tube 18 using cross-head extruder 48.Thereafter, cable 50 passes into a second water trough 46 before beingwound-up on take-up reel 49. Additionally, other cables and/ormanufacturing lines according to the concepts of the present inventionare possible. For instance, cables and/or manufacturing lines mayinclude a water-swellable tape 19 c and/or an armor between tube 18 andstrength members 19 a; however, the use of other suitable cablecomponents are possible.

FIG. 6 is a graph depicting the results of a ribbon coupling force forcables having the similar tube assemblies as used in FIG. 3. The ribboncoupling force test is used for modeling the forces applied to theoptical waveguide(s) when subjecting a cable to, for example, pullingduring installation of the cable. Although the results between theribbon pullout force and the ribbon coupling force may have forces inthe same general range, the ribbon coupling force is generally a betterindicator of actual cable performance.

In this case, the ribbon coupling test simulates an underground cableinstallation in a duct by applying 600 pounds of tension on a 250 mlength of cable by placing pulling sheaves on the respective sheathes ofthe cable ends. However, other suitable loads, lengths, and/orinstallation configurations can be used for characterizing ribboncoupling in other simulations. Then, the force on the opticalwaveguide(s) along its length is measured from the end of cable. Theforce on the optical waveguide(s) is measured using a Brillouin OpticalTime-Domain Reflectometer (BOTDR). Determining a best-fit slope of thecurve normalizes the ribbon coupling force.

As a baseline for comparison, curve 60 depicts a normalized ribboncoupling force of about 1.75 N/m for a cable having a ribbon stack of120-fibers in conventional grease filled cable (FIG. 11). Curve 62depicts a ribbon pullout force for a cable having a conventional drytube design having a water-swellable tape around a ribbon stack of144-fibers (FIG. 12), which are loosely disposed in a tube.Specifically, curve 62 depicts a normalized ribbon coupling force ofabout 0.15 N/m for the 144-fiber ribbon stack. Thus, the conventionaldry tube design (FIG. 12) has a normalized ribbon coupling force that isabout nine percent of the normalized ribbon coupling force of theconventional grease filled tube (FIG. 11), which is inadequate forproper cable performance. In other words, the ribbon stack of theconventional dry tube cable is easily displacable during stretching ofthe cable sheath, for example, during aerial ice loading, aerialgalloping, cable dig-ups, and pulling during installation of the cable.

Curves 64, 66, and 68 represent cables according to the presentinvention. Specifically, curve 64 depicts a ribbon coupling force of acable having a 144-fiber stack with a tube assembly 10 having dry insert14 with an uncompressed height h of about 1.5 mm with about a zeropercent compression of dry insert 14. In this embodiment, curve 64depicts a ribbon coupling force of about 0.80 N/m, which is animprovement over the conventional dry cable of FIG. 12. Curves 66 and 68represent cable configurations where dry insert 14 is compressed withintube assembly 10 by a percentage from its original height to an averagecompressed height. More specifically, curve 66 represents a ribboncoupling force of a similar cable as curve 64, expect that in thisembodiment dry insert 14 is compressed about thirty percent. In thisembodiment, curve 66 depicts a ribbon coupling force of about 2.80 N/m.Curve 68 represents a ribbon coupling force of a cable having a144-fiber ribbon stack from a cable having a tube assembly with dryinsert 14 having an uncompressed height h of about 3 mm, which iscompressed by about thirty percent within the tube. In this embodiment,curve 68 depicts a ribbon coupling force of about 0.75 N/m. Thus,according to the concepts of the present invention the ribbon couplingforce is preferably in the range of about 0.5 N/m to about 5.0 N/m, morepreferably, in the range of about 1 N/m to about 4 N/m. However, othersuitable ranges of ribbon coupling force may provide the desiredperformance.

Additionally, the concepts of the present invention can be employed withother configurations of the dry insert. As depicted in FIG. 7, dryinsert 74 has a first layer 74 a and a second layer 74 b that includesdifferent suitable types of water-swellable substances. In oneembodiment, two different water-swellable substances are disposed in, oron, second layer 14 b so that tube assembly 10 is useful for multipleenvironments and/or has improved water-blocking performance. Forinstance, second layer 14 b can include a first water-swellablecomponent 76 effective for ionized liquids such as saltwater and asecond water-swellable component 78 effective for non-ionized liquids.By way of example, first water-swellable material is a polyacrylamideand second water-swellable material is a polyacrylate superabsorbent.Moreover, first and second water-swellable components 76, 78 can occupypredetermined sections of the water-swellable tape. By alternating thewater-swellable materials, the tape is useful for either standardapplications, salt-water applications, or both. Other variations ofdifferent water-swellable substances include having a water-swellablesubstance with different swell speeds, gel strengths and/or adhesionwith the tape.

FIG. 8 depicts another embodiment of the dry insert. Dry insert 84 isformed from three layers. Layers 84 a and 84 c are water-swellablelayers that sandwich a layer 84 b that is compressible for providing acoupling force to the at least one optical waveguide. Likewise, otherembodiments of the dry insert can include other variations such at leasttwo compressible layers sandwiching a water-swellable layer. The twocompressible layers can have different spring constants for tailoringthe normal force applied to the at least optical waveguide.

FIG. 9 illustrates a dry insert 94 having layers 94 a and 94 b accordingto another embodiment of the present invention. Layer 94 a is formedfrom a closed-cell foam having at least one perforation 95 therethroughand layer 94 b includes at least one water-swellable substance; however,other suitable materials can be used for the compressible layer. Theclosed-cell foam acts as a passive water-blocking material that inhibitswater from migrating therealong and perforation 95 allows an activatedwater-swellable substance of layer 94 b to migrate radially inwardtowards the optical waveguide. Any suitable size, shape, and/or patternof perforation 95 that allows the activated water-swellable substance tomigrate radially inward to effectively block water is permissible. Thesize, shape, and/or pattern of perforations can be selected and arrangedabout the corner optical waveguides of the stack, thereby improvingcorner optical waveguide performance. For example, perforations 95 canprovide variation in dry insert compressibility, thereby tailoring thenormal force on the optical waveguides for maintaining opticalperformance.

FIG. 10 depicts dry insert 104, which illustrates other concepts of thepresent invention. Dry insert 104 includes layers 104 a and 104 b. Layer104 a is formed of a plurality of non-continuous compressible elementsthat are disposed on layer 104 b, which is a continuous water-swellablelayer. In one embodiment, the elements of layer 104 a are disposed atregular intervals that generally correlate with the lay length of aribbon stack. Additionally, the elements have a height h that variesacross their width w. Stated another way, the elements are shaped toconform to the shape of the optical waveguides they are intended togenerally surround.

Many modifications and other embodiments of the present invention,within the scope of the appended claims, will become apparent to askilled artisan. For example, optical waveguides can be formed in avariety of ribbon stacks or configurations such as a stepped profile ofthe ribbon stack. Cables according to the present invention can alsoinclude more than one optical tube assembly stranded helically or in S-Zconfigurations. Additionally, dry inserts of the present invention canbe laminated together as shown or applied as individual components.Therefore, it is to be understood that the invention is not limited tothe specific embodiments disclosed herein and that modifications andother embodiments may be made within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation. Theinvention has been described with reference to silica-based opticalwaveguides, but the inventive concepts of the present invention areapplicable to other suitable optical waveguides and/or cableconfigurations. For instance, dry inserts of the present invention aresuitable for use in tubeless cables with a sheath therearound.

1. An optical tube assembly comprising: a tube, the tube having aninterior surface; at least one optical waveguide, the optical waveguidebeing disposed in the tube; and at least one dry insert, the at leastone dry insert being disposed within the tube generally adjacent to theinterior surface of the tube and surrounding the at least one opticalwaveguide, the at least one dry insert being compressed at least 10percent for coupling the at least optical waveguide to the interiorsurface of the tube.
 2. The optical tube assembly of claim 1, thecompression of the foam tape being about 90% or less.
 3. The opticaltube assembly of claim 1, the at least one dry insert comprising acompressible layer and at least one water-swellable layer.
 4. Theoptical tube assembly of claim 1, the water-swellable layer being awater-swellable tape.
 5. The optical tube assembly of claim 4, thewater-swellable tape having a first water-swellable component and asecond water-swellable component.
 6. The optical tube assembly of claim5, the first water-swellable component being effective for ionizedliquid and the second water-swellable component being effective fornon-ionized liquid.
 7. The optical tube assembly of claim 1, the atleast one dry insert being attached to the tube.
 8. The optical tubeassembly of claim 1, the at least one dry insert comprising a pluralityof non-continuous compressible elements disposed on a water-swellabletape.
 9. The optical tube assembly of claim 1, the at least one dryinsert comprising a compressible layer and at least one water-swellablelayer, the compressible layer having a non-uniform height across itswidth.
 10. The optical tube assembly of claim 1, the at least oneoptical waveguide having a normalized pull-out force between about 0.5N/m and about 5.0 N/m.
 11. The optical tube assembly of claim 1, the atleast one optical waveguide having a normalized pull-out force betweenabout 1 N/m and about 4 N/m.
 12. The optical tube assembly of claim 1,the at least one dry insert being a composite tape having a foam layerand a water-swellable layer, the composite tape having an uncompressedheight of about 5 mm or less.
 13. The optical tube assembly of claim 1,a portion of the at least one dry insert having at least oneperforation.
 14. The optical tube assembly of claim 1, the at least onedry insert being formed from at least two layers.
 15. The optical tubeassembly of claim 1, the optical tube assembly being a portion of afiber optic cable.
 16. The optical tube assembly of claim 15, the fiberoptic cable having a normalized ribbon coupling force between about 0.5N/m and about 5 N/m.
 17. The optical tube assembly of claim 1, the dryinsert at least partially contacting the at least one optical waveguide.18. An optical tube assembly comprising: a tube, the tube having aninterior surface; at least one optical waveguide; and at least one dryinsert, the at least one dry insert having at least two laminated layersgenerally surrounding the at least one optical waveguide, therebyforming a core that is disposed within the tube, the dry insertcomprising a compressible layer and at least one water-swellable layerand the at least one dry insert acts to couple the at least one opticalwaveguide to the interior surface of the tube while cushioning the atleast one optical waveguide, thereby maintaining an optical attenuationbelow about 0.4 dB/km at a reference wavelength of 1310 nm.
 19. Theoptical tube assembly of claim 18, the compressible layer being a foamtape that is compressed by about 10% or more.
 20. The optical tubeassembly of claim 18, the compressible layer being a foam tape that iscompressed by about 90% or less.
 21. The optical tube assembly of claim18, the water-swellable layer being a water-swellable tape.
 22. Theoptical tube assembly of claim 18, the water-swellable layer having afirst water-swellable component and a second water-swellable component.23. The optical tube assembly of claim 22, the first water-swellablecomponent being effective for ionized liquid and the secondwater-swellable component being effective for non-ionized liquid. 24.The optical tube assembly of claim 18, the at least one dry insert beingattached to the tube.
 25. The optical tube assembly of claim 18, the atleast one dry insert comprising a plurality of non-continuouscompressible elements disposed on a water-swellable tape.
 26. Theoptical tube assembly of claim 18, the compressible layer having anon-uniform height across its width.
 27. The optical tube assembly ofclaim 18, the at least one optical waveguide having a normalizedpull-out force between about 0.5 N/m and about 5.0 N/m.
 28. The opticaltube assembly of claim 18, the at least one optical waveguide having anormalized pull-out force between about 1 N/m and about 4 N/m.
 29. Theoptical tube assembly of claim 18, the at least one dry insert having anuncompressed height of about 5 mm or less.
 30. The optical tube assemblyof claim 18, a portion of the at least one dry insert having at leastone perforation.
 31. The optical tube assembly of claim 18, the at leastone dry insert being formed from more than two layers.
 32. The opticaltube assembly of claim 18, the optical tube assembly being a portion ofa fiber optic cable.
 33. The optical tube assembly of claim 32, thefiber optic cable having a normalized ribbon coupling force betweenabout 0.5 N/m and about 5 N/m.
 34. The optical tube assembly of claim18, the dry insert at least partially contacting the at least oneoptical waveguide.
 35. An optical tube assembly comprising: a tube, thetube having an interior surface; at least one optical waveguide; and atleast one dry insert, the at least one dry insert comprising acompressible layer and at least one water-swellable layer, wherein theat least one dry insert and the at least one optical waveguide form acore disposed within the tube, wherein the at least one opticalwaveguide has a normalized pull-out force between about 0.5 N/m andabout 5.0 N/m when pulled from the at least one dry insert.
 36. Theoptical tube assembly of claim 35, the normalized pull-out force beingbetween about 1 N/m and about 4 N/m.
 37. The optical tube assembly ofclaim 30, the compressible layer being a foam tape that is compressed byabout 10% or more.
 38. The optical tube assembly of claim 35, thecompressible layer being a foam tape that is compressed by about 90% orless.
 39. The optical tube assembly of claim 35, the water-swellablelayer being a water-swellable tape.
 40. The optical tube assembly ofclaim 35, the water-swellable layer having a first water-swellablecomponent and a second water-swellable component.
 41. The optical tubeassembly of claim 40, the first water-swellable component beingeffective for ionized liquids and the second water-swellable componentbeing effective for non-ionized liquids.
 42. The optical tube assemblyof claim 35, the at least one dry insert being attached to the tube. 43.The optical tube assembly of claim 35, the at least one dry insertcomprising a plurality of non-continuous compressible elements disposedon a water-swellable tape.
 44. The optical tube assembly of claim 35,the at least one dry insert having an uncompressed height of about 5 mmor less.
 45. The optical tube assembly of claim 35, the compressiblelayer having a non-uniform height across its width.
 46. The optical tubeassembly of claim 35, a portion of the at least one dry insert having atleast one perforation.
 47. The optical tube assembly of claim 35, the atleast one dry insert being formed from at least two layers.
 48. Theoptical tube assembly of claim 35, the optical tube assembly being aportion of a fiber optic cable.
 49. The optical tube assembly of claim48, the fiber optic cable having a normalized ribbon coupling forcebetween about 0.5 N/m and about 5 N/m.
 50. A method of manufacturing anoptical tube assembly comprising: paying off at least one opticalwaveguide; placing at least one dry insert adjacent to the at least onewaveguide, thereby forming a core, wherein the at least one dry insertcomprises a compressible layer and at least one water-swellable layer;and extruding a tube around the core, wherein the at least one opticalwaveguide has a normalized pullout force between about 0.5 N/m and about5.0 N/m.
 51. The method of claim 50, the normalized pullout force beingbetween about 1 N/m and about 4 N/m.
 52. The method of claim 50, thestep of placing comprising wrapping at least one dry insert about the atleast one optical waveguide so that it at least partially contacts theat least one optical waveguide.
 53. The method of claim 50, the at leastone dry insert having at least one perforation.
 54. The method of claim50, further comprising the step of securing the core with a binderthread.
 55. The method of claim 50, further comprising the step ofcompressing the at least one dry insert.
 56. The method of claim 50, theat least one optical waveguide maintaining an optical attenuation ofbelow about 0.4 dB/km from the group of reference wavelengths selectedfrom 1310 nm, 1550 nm, and 1625 nm.
 57. The method of claim 50, the atleast one dry insert comprising a foam tape and a water-swellable layer.58. The method of claim 50, the compressible layer having a non-uniformheight across its width.
 59. The method of claim 50, further comprisingthe steps of placing at least one strength member adjacent to the tubeand extruding a jacket therearound, thereby forming a fiber optic cable.60. The optical tube assembly of claim 59, the fiber optic cable havinga normalized ribbon coupling force between about 0.5 N/m and about 5N/m.